1. Field of the Invention
This invention relates to a drive circuit for sounders having a resonant frequency such as piezo-electric buzzers and microphones.
2. Description of the Prior Art
Such sounders, because of their small size and light weight, have found many uses in various fields of art, for example, in cameras and sound instruments. There is a high probability that they will be used in the near future even in the art of motion picture instruments such as video cameras.
A technique in which the out-of-range low light value is indicated by a sound signal from the speaker built into the camera is described in German Pat. No. 1297461.
Another technique in which a plurality of sound signals are formed by one sounder, and, as the sound type is changed, a plurality of warning signals are controlled is shown in U.S. Pat. No. 3,872,470.
Furthermore, even in the camera art, the audio warning signal representing filming end is disclosed in U.S. Pat. Nos. 3,776,652, and 4,272,176 discloses a single sounder providing different audio signals a self-timer-under-operation signal and an out-of-range low brightness signal.